1. Field of the Invention
The present invention generally relates to a video camera operable with either a VHS magnetic recording tape or a 8 mm magnetic recording tape and, more particularly, to the video camera equipped with means for disabling an uncalled-for recording in the event that a video camera continues video recording against the will of an operator such as when the operator inadvertently fails to switch the video camera off.
For the purpose of the present invention, the means for disabling an uncalled-for recording in the event that video camera continues video recording against the will of an operator will be referred to as a "record shutoff mechanism".
2. Description of the Prior Art
Video cameras equipped with a record shutoff mechanism, i.e., means for disabling an uncalled-for recording in the event that the video camera continues video recording against the will of an operator, are well known and prior art examples of record shutoff mechanisms are disclosed in, for example, the Japanese Laid-open Patent Publications No. 2-87875 and No. 3-274969.
The record shutoff mechanism disclosed in the Japanese Laid-open Patent Publication No. 2-87875 comprises a detector means for detecting a change of a portion or the whole of the viewed image of an object being videoed, a determining means operable in response to information provided by the detecting means to determine whether or not the viewed image has actually changed within the framework of a viewfinder screen and then to provide an output only when it has determined the viewed image having been changed, and a disabling means operable in response to the output from the determining means to disable a video recording operation of the video camera.
The record shutoff mechanism disclosed in the Japanese Laid-open Patent Publication No. 3-274969 includes either one of a photoelectric sensor or a touch-sensor installed at an eyepiece area of the viewfinder. In one embodiment where the photoelectric sensor is employed, the photoelectric sensor is utilized to determine whether or not an operator of the video camera is viewing the image cast on the viewfinder screen with his or her eye close towards the eyepiece and then to provide an output necessary to disable the operation of the video camera when the photoelectric sensor determines that the operator's eye is substantially distant from the eyepiece of the viewfinder. In the different embodiment where the touch-sensor is employed, the touch-sensor is utilized to determine whether or not an operator of the video camera is viewing the image cast on the viewfinder screen with his or her eye held in contact with an eyepiece area of the viewfinder and then to provide an output necessary to disable the operation of the video camera when the touch-sensor determines that the operator's eye is substantially distant from the eyepiece of the viewfinder.
Video cameras currently available in the market have, in addition to a power control switch, a REC (RECORD) button which is generally in the form of a toggle button capable of selectively assuming one of two different positions, a REC position to initiate a video recording and a STOP position to halt the video recording, for ease of camera handling. More specifically, commercially available video cameras are such that, when the power control switch is turned on, the video camera is held at a STAND-BY position in readiness for actual video recording which subsequently takes place upon manipulation (either slide or push) of the REC button to assume the REC position. In some of the video cameras, the STAND-BY position means that a length of magnetic recording tape is turned around a head-carrier cylinder so that the video recording can be quickly initiated immediately after manipulation of the REC button to assume the REC position. The video recording can be terminated when the REC button is again manipulated, but to assume the STOP position.
With those types of video cameras, it is not unusual that the operator fails to move the REC button to the STOP position and allows the video camera to continue its recording operation without realizing that the REC button in the REC position has not yet been moved to the STOP position. This uncalled-for video recording results in an unnecessary take-up of a substantial length of magnetic recording tape with no significant image recorded thereon and an unnecessary waste of the very limited battery power and it often occurs that, next time the operator intends to make a video recording, the video camera will no longer work because no more tape is available and/or because of a shortage of battery power.
In view of the generalities of the video cameras as discussed above, the record shutoff mechanism such as disclosed in the Japanese publications referred to above appears to be a convenient instrument. However, the record shutoff mechanism disclosed in the No. 2-87875 publication has been found having a problem in that, particularly where still-frame video images are being taken in succession with the video camera installed on a tripod, the record shutoff mechanism will work in response to the change of the viewed image to halt the recording operation against the will of an operator. Another problem associated with this known record shutoff mechanism is that, if the operator hailing to move the REC button to the STOP position walks around with the video camera hung from the shoulder, the video camera is correspondingly shaken to such an extent as to result in a considerable change of an image signal for one field or one frame, thereby fooling the record shutoff mechanism, that is, rendering the record shutoff mechanism to be ineffective to stop the video recording.
On the other hand, even the record shutoff mechanism disclosed in the No. 3-274969 publication has problems in that, in the event that the operator remove his or her eye away from the eyepiece area of the viewfinder for visual inspection of the object being videoed or for any other reason, the record shutoff mechanism immediately works to stop the video recording against the operator's will and in that, since the record shutoff mechanism works immediately after the operator removes his or her eye away from the viewfinder, a high-angle video recording with the video camera held overhead is impossible.